Citraconic anhydride is a useful intermediate for the curing of epoxy resins.
U.S. Pat. NO. 2,966,498 describes a method for the production of citraconic anhydride by heating itaconic acid in the presence of an alkali metal dihydrogen phosphate or sulfate at elevated tempertures.
The preparation of citraconic acid by the vapor phase catalytic dehydration and decarboxylation of related six-carbon acids such as citric acid, isocitric acid, aconitic acid and mixtures thereof is described in U.S. Pat. No. 3,701,805.
In a process reported by Kunichika, S., Oka, S., Tanaki, H., in Bull. Inst. Chem. Res., Kyoto University 44, No. 3, 221-225 (1966), citraconic acid was prepared by the pyrolysis of the acetate of the anhydride of citramalic acid.